From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 4F03C3858416; Wed, 22 May 2024 08:49:53 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4F03C3858416
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1716367793;
	bh=F4zWgGqodCE0jlnAlwYYe/mCKWrCJp87jnAJV20Ee5E=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=tTU/zvljgNWq/PhoRY+XepjevzngoSgs1CsYpM7AssQ2R8qstimLAaCkyk0jZp3s3
	 c53nG7ON9ElqLsqA+NAQemFRq0/VhM12LFjt/EQrlf2PELILfzZFhWrQfE2SwgcjSh
	 Wy/A799x7pVh7E6NWcnXgK+cTh84m687O/R9lpwE=
From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/115161] [15 Regression] highway-1.0.7 miscompilation of
 some SSE2 intrinsics
Date: Wed, 22 May 2024 08:49:51 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 15.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: amonakov at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 15.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-115161-4-jc6BXbA44z@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-115161-4@http.gcc.gnu.org/bugzilla/>
References: <bug-115161-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115161

--- Comment #20 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #19)
> If we guarantee that we never constant fold FIX/UNSIGNED_FIX with
> -ftrapping-math (we shouldn't, as the exceptions should be raised), then
> using FIX/UNSIGNED_FIX is ok in
> flag_trapping_math guarded patterns even if the intrinsics have some
> specific value they want in those cases, because they will never be folde=
d.

No, this sounds illogical. The compiler may fold out-of-range conversions j=
ust
fine, it just needs to preserve the original operation (with its result now
dead), or use any other opportunity to ensure that exceptions are still rai=
sed.
Specifically, it is okay to transform

float f;
int i;

f =3D 0x0.8p+33f;
i =3D (int) f;

to

f =3D 0x0.8p+33f;
dummy =3D (int) f;
i =3D INT_MAX; // or whatever

The "known" value of 'i' may then facilitate further folding.=